8.6 blackout

[BountyHunter]

Been playing with a faxon bolt 8.6 blackout. in MDT stock and timney trigger. Tried the 300 Maker and after, 60 bullets, 4 powders, 4 primers came to conclusion that this barrel does not like the maker 300. Best group was about 4 inches at 100, with some over 12 inches.

Tried some factory 285 Gorilla and gun obviously loves them. Test to see with barrel was any good. Factory was around 988 fps and 1.5 inches. Worked out that with Gorilla 285, BR2 primers and LiL Gun from 13.4-13.6 and results were 1.5-2 inch groups and MV 1060 to 1045. Used Nomax 33 and super quiet.

Interesting side note that Faxon is sensitive to primer seating depth and likes them seated really deep with no space.

That 1-3 twist at supersonic is very hard on jacketed bullets. They come apart.

 

[ELR LVR]

is that the 1:3 twist Faxon barrel?

 

[BountyHunter]

is that the 1:3 twist Faxon barrel?

yes Faxon action and barrel. 8.6 BO is using very fast 1-3 twist.

 

[ELR LVR]

I chambered one of those barrels in same caliber for a friend
We were both surprised at the twist rate when a lot of people were using a 1:6 twist -Even with the heavies
Wondering if the extremely fast twist makes it finicky
---
I will say the barrel felt and machined nicely, as if the steel quality is good

 

[Oso]

There is a reason that only solid copper bullets are recommended for use in 8.6BO (1:3 twist). There are reports of cup/core bullets exiting the barrel as fragments (catastrophic failure) that have damaged suppressors. A 1:5 twist is sometimes used to improve accuracy, especially for supersonic. I have been looking for more field tests on 1:5 twist or 1:6 twist to see how they handle traditional bullets.

Q decided to stick with a 1:3 twist for their 8.6 Blackout rifles. This meant that none of the bullets manufactured by Hornady were capable of handling the high rpm. It sure looks like Hornady rushed to develop and introduce the 338ARC recommending a 1:8 twist. This twist rate would ensure that any/all of their bullets (copper jacket with lead core) would perform without risk of catastrophic fear failure.

I keep waiting to see more gel test featuring Hornady SubX bullet out of 1:5 twist.

 

[rickiesrevenge]

I've got a piece of 4t pacnor barrel. Haven't decided exactly what I want to build yet. I do have an 8.6bo reamer but nothing other than that.

 

[BountyHunter]

There is a reason that only solid copper bullets are recommended for use in 8.6BO (1:3 twist). There are reports of cup/core bullets exiting the barrel as fragments (catastrophic failure) that have damaged suppressors. A 1:5 twist is sometimes used to improve accuracy, especially for supersonic. I have been looking for more field tests on 1:5 twist or 1:6 twist to see how they handle traditional bullets.

Q decided to stick with a 1:3 twist for their 8.6 Blackout rifles. This meant that none of the bullets manufactured by Hornady were capable of handling the high rpm. It sure looks like Hornady rushed to develop and introduce the 338ARC recommending a 1:8 twist. This twist rate would ensure that any/all of their bullets (copper jacket with lead core) would perform without risk of catastrophic fear failure.

I keep waiting to see more gel test featuring Hornady SubX bullet out of 1:5 twist.

I can also confirm the cup/core bullets will come apart and damage suppressors. That 1-3 will flat tear them apart.

 

[dellet]

Which 300 grain Maker?
The target bullet or the expanding?

 

[BountyHunter]

expanding. This Faxon barrel just did not like them. 285 gorilla expanding works.

 

[dellet]

expanding. This Faxon barrel just did not like them. 285 gorilla expanding works.

1/3 twist is hard on bullets, you might confirm the twist.
A couple things come to mind. First is to make sure you have the right bullet. Maker has 2 300 grain .338 bullets, make sure you have the correct one for the 8.6 1/3. If it is the correct one, limit the velocity to 1000-1025. It’s very rare that a max velocity is posted for a bullet, but 1050 is listed as max for 8.6 expanding bullet. Lilgun can be erratic, give yourself some room.

I’m sure you probably tried 296/H110, if not, it’s worth visiting. 300MP if you can find it is another good choice.

A faster powder can help prevent gas cutting the base of the bullet which is fairly common with copper solid subs, in a 1/3 it may cause the bullet to be compromised on starting down the bore. It may start to open up due to the front skived halve starting to twist before the solid base. That might be worth exploring without the suppressor attached.

Maybe a couple different things you might not have tried.